China's Tencent Holdings Ltd has suspended more than 300 accounts on its WeChat mobile messaging app and banned around 40 others as government restrictions on spreading political news online take effect, state media said on Friday.

Earlier this month, China imposed new rules on what kind of information can be spread via instant messaging apps as well as restrictions on accounts which can broadcast news to large numbers of followers.

Of the 357 accounts closed down by Tencent as of August 25, 46 were permanently banned while the rest were suspended, the official Xinhua news agency said on its microblog.

According to the new restrictions, the providers of instant messaging tools like Tencent must enforce the regulations themselves.

A Tencent spokeswoman declined to provide immediate comment.

Observers say President Xi Jinping is presiding over the worst crackdown on the internet and online censorship in China in recent memory. Xi also heads the Central Internet Security and Informatisation Leading Group, an internet security body whose remit includes building China into a cyber power, according to state media.

Gary King, a professor at Harvard University who researches China's internet censorship, said earlier this week the ruling Communist Party was particularly concerned about the dissemination of messages which could lead to social unrest or collective action.

Social media was a catalyst for the political revolutions that took place in countries like Egypt and Tunisia in the last few years.

Earlier this month, Chinese authorities for the first time detained a man for spreading panic on WeChat mere hours after the new rules on instant messaging took effect.